A multi-layer wiring structure is employed so as to implement highly-integrated semiconductor devices. In order to constitute the multi-layer wiring structure, adjacent wiring layers are connected by a conductive layer, and regions other than the conductive layer need to be insulated by an interlayer dielectric film. Conventionally, SiO2 layer is widely used as the interlayer dielectric film. However, in these days, in order to reduce the capacity between wiring layers so as to manufacture fine and high-speed semiconductor devices, the interlayer dielectric film needs to have low permittivity.
As the interlayer dielectric film having low permittivity, a fluorine-added carbon film (fluoro carbon film: CFx film) that is a compound of carbon (C) and fluorine (F) has been highlighted. Relative permittivity of 2.5 or less for the fluorine-added carbon film may be attained by selecting the type of a raw material gas in contrast with the SiO2 layer having relative permittivity of about 4. Thus, the fluorine-added carbon film is very effective for obtaining an interlayer dielectric film having low permittivity. Recently, a chemical vapor deposition (CVD) apparatus that generates plasma with low electron temperature by selecting a raw material gas or with high density has been developed so that a better layer can be obtained and will be put to practical use.
As a method of etching the fluorine-added carbon film, a method by which a hydrogen gas and a nitrogen gas are plasmatized and the fluorine-added carbon film is etched by using plasma of the hydrogen gas and the nitrogen gas, has been known (Materials Research Society Conference Proceedings, Volume V-14, Advanced Metallization Conference in 1998). However, when the above method is performed, hydrogen is introduced into side wall portions of the etched fluorine-added carbon film and is combined with fluorine in the fluorine-added carbon film, so that hydrogen fluoride can be generated and the fluorine-added carbon film may be damaged. In addition, in a following process, a barrier metal layer is formed in an etched recess portion, or metal is buried therein. However, if hydrogen fluoride is generated, the barrier metal layer or metal is corroded and damaged, and thus, an adhesiveness of the fluorine-added carbon film and the barrier metal layer or metal to each other is degraded.
In order to solve the problem, a technology for etching a fluorine-added carbon film by using plasma of a process gas including a CxFy (where x and y are natural numbers) gas, such as a CF4 gas, has been suggested (Japanese Laid-open Patent Publication No. 2005-123406). Thus, the fluorine-added carbon film can be etched with low damage.
However, if the fluorine-added carbon film is etched by using a CxFy-containing gas, such as a CF4 gas, an etching selectivity with respect to a hard mask layer, such as SiN or SiCN, used as an etching mask, is low, and the shape of processing the fluorine-added carbon film is not good.